1. Field of the Invention
This invention relates to polyisocyanate reaction products and, more particularly, to the reaction product of polyisocyanates and tanned leather scrap.
2. Description of the Prior Art
Polyisocyanates are known for their reactivity with a variety of functional groups and have been used in forming coatings, foams, laminates, and other articles of manufacture. The most extensive use of polyisocyanates has been in the formation of polyurethanes which are typically the reaction product of a polyisocyanate and a polyhydroxy compound. Further, it has been known that polyisocyanates, through the isocyanate group, are reactive with carboxyl groups, water, and amine groups to form ureas, biurets and mixed urethanes.
In one particular use of polyisocyanates, such polyisocyanates are reacted with sawdust, wood chips and the like under heat and pressure to form what is known as "particle board" or "chip board". This particle board or chip board has found extensive utility in the construction and furniture industry since in many instances its physical properties are similar to that of expensive hard woods and when finished in the appropriate manner have comparable aesthetic properties. Further, this particle board or chip board is structurally sound and is useful in a broad range of applications.
Another advantage of a particle board or chip board is that the cost of manufacture and raw materials is substantially less than that of board stock. The diminishing supply of wood has caused wood to become extremely expensive in comparison with other construction materials. The use of wood chips and/or sawdust which are by-products of the milling process provide material, which is low in cost, and once reacted with polyisocyanates under heat and pressure form desirable products.
One of the deficiencies of chip board and/or particle board is that they readily burn because of the high cellulosic content and in order to impart fire retardant characteristics to the chip board or particle board, it is necessary to incorporate fire retardant additives therein. These fire retardant additives are typically halogen and phosphorus containing materials and may also contain antimony and a variety of other speciality chemicals which increase the cost of the particle board or chip board thus making such material undesirable.
The industry has long pursued production of a product which is low in cost yet has the integrity and workability of chip board or particle board or wood and which has fire retardant characteristics while maintaining a lot cost of production.
In accordance with the present invention, an article of manufacture is provided which is comparable in integrity, workability and economic advantage while providing the added advantage of inherent fire retardancy.